Heat exchangers of the above type are already known which comprise a bundle of tubes which are mounted between two water boxes or manifolds, each of which is delimited by a wall of moulded plastics material having two opposed lateral faces on which two mountings are fitted. Each of these mountings has a U-shaped transverse cross section, and joins the two water boxes together while the two mountings enclose the tube bundle between them. Each mounting comprises a body portion or web from which two side portions extend.
The two mountings which join the water boxes together thus give the heat exchanger a high mechanical strength, which enables the heat exchanger to be made large so as to be suitable for mounting on a motor vehicle, and in particular a heavy goods vehicle. This is important because in such circumstances it is subjected in operation to high mechanical stresses, due in particular to engine vibrations and to variations in thermal expansion of the tubes in the bundle.
It is known, from the specification of European patent No. 115 795, to build such a heat exchanger in which each of the mountings is secured on each of the water boxes by means of at least one dowel or pin which passes right through the water box and through two apertures which are formed in the two opposed lateral portions of the mounting. Fitting of such dowels is complex and costly in practice.
It is also known from European patent No. 112 251 to construct a heat exchanger of similar type, in which the water boxes are made of cast metal, and in which the appropriate portions of a mounting are secured on a lateral face of a water box by means of at least one bolt which passes through an aperture formed in that portion of the mounting, being screwed into a threaded hole, which is provided for this purpose within the thickness of the water box wall. Here again, however, the fastening operation is time-consuming and expensive to carry out, because it requires two successive machining operations on each water box so as initially to form in it a plurality of holes or apertures, and this has to be followed by threading operations.